Magnetic tape cassette recorders typically incorporate a mechanism that senses whether a record opening in a wall of the cassette is blocked or unblocked. When the opening is unblocked, the recording function is disabled to prevent accidental erasure. U.S. Pat. No. 4,875,109, issued to Hanson, one of the inventors of this invention, and assigned to the Minnesota Mining and Manufacturing Co., the assignee of this invention, describes a pivoting recording latch which performs this function.
The '109 recording cassette has a record opening in a bottom wall of the cassette and a web extending from the top wall of the cassette. The web partially closes a latch-engaging opening. The latch is pivotable between two positions and a plug at one end of the latch either blocks or unblocks the record opening while a flange at the other end of the latch is either visible or not visible at the latch-engaging opening in the top wall to indicate the record status. When the flange is visible it covers the web and when it is not visible it uncovers the web. The exposed face of the flange has a cavity into which a point can be inserted to pivot the latch. However, the '109 latch is secured in the record position in the top wall of the cassette while the latch is secured in the no-record position in the bottom wall of the cassette. As there is positional shifting of the top and bottom walls during assembly, uniformity of latching can be lost from one cassette to the next.